Abstract

Inactivity, as it appears during space flight and in bed rest, induces reduction of lean body and bone mass, glucose intolerance, and weakening of the cardiovascular system. Increased protein intake, whey protein in particular, has been proposed to counteract some of these effects, but has also been associated with negative effects on bone, likely caused by a correspondingly high ratio of acid to alkali precursors in the diet.
The main hypothesis of the presented cross-over study (MEP study) was that supplementing high protein intake (1.2 g/kg body weight/d plus 0.6 g/kg body weight/d whey protein) with alkaline salts (90 mmol potassium bicarbonate/d) will maintain lean body mass during bed rest without increasing bone resorption. A 21-day head-down-tilt bed rest study was performed to examine several physiological systems in a multidisciplinary approach. Ten healthy men (age: 31±6 years; body weight: 76.5±5.6 kg) were randomly assigned to the dietary countermeasure or isocaloric control first, one test subject randomized to the dietary countermeasure first dropped out after the first campaign.